ABSTRACT
Eukaryotes have a remarkably well-conserved apparatus for the trafficking of proteins between intracellular compartments and delivery to their target organelles (a process termed “protein kinesis”). This apparatus comprises the secretory (or “protein export”) pathway, which is responsible both for the proper processing and delivery of proteins and lipids, and is essential for the derivation and maintenance of organelles. Even in the most simplistic terms, the mechanics of delivering a mature protein to a target compartment requires an elaborate system of selective protein capture, processing, packaging, and targeting. Moreover, as the nature of this system is bidirectional, it allows for the retrieval and re-use of specific trafficking components, and helps maintain the distinct molecular identity of each intracellular compartment along the pathway. Thus, an essential, highly complex, apparatus for ensuring the fidelity of protein targeting and delivery has evolved to fit the needs of both unicellular and multicellular organisms. Moreover, ongoing studies of protein kinesis reveal that despite several billion years of eukaryote evolution, not all that much has changed mechanistically and that both higher and lower organisms use similar processing and export strategies.
